Shell structure for stairsteps



United States Patent O 3,389,523 SHELL STRUCTURE FOR STAIRSTEPS Ubaldo Bertel, Via Garibaldi 19, Verona, Italy Filed Dec. 14, 1964, Ser. No. 418,109 Claims priority, application Italy, Oct. 26, 1964, 23,078/ 64 2 Claims. (Cl. 52-606) The present invention is related to preformed shell structures for use as individual steps in the erection of conventional stairs and, more particularly, it is related to preformed cementitious shell structures, such as of brick, tile or other similar and/ or equivalent material.

It is well known that any two fully superimposed or partially superimposed floors, contained within the walls of a building, are connected by a series of flights of stairs, each flight connecting, generally, two adjoining landings or stair heads and being composed of a predetermined number of steps, each step being formed by the so-called riser and tread. In a rectilinear or straight flight, the steps are constructed on rectangular plans, leaving any irregularity of the masonry work to the landings or stair heads.

The variety of techniques in stairbuilding, using various types of steps, is well known. Besides the typically classical massive steps, the step-building technique has brought improvements to the art of stair construction by adopting, in recent years, single planar slabs of reinforced concrete embedded in the masonry or in the oversailing courses and, still more recently, by utilizing steps formed of triangular elements which are monolithic, self-supporting, in relief and pre-laid.

It is evident, however, that these triangular elements, because of their very nature, are very heavy due to the considerable volume of concrete therein and are very expensive due to the proportionately high quantity of metallic reinforcement therein.

It has now been found that these disadvantages may be readily overcome by constructing a stairstep structure which, while following the ideal triangular element of the monolithic steps of reinforced concrete, is prepared from shelled tiles or bricks or equivalent material. This novel structure of the invention contains amid its reticulated interior a leak-proof chamber suitable for receiving and containing a load of freshly-introduced concrete into which the reinforcing steel can be immersed.

The light weight of the novel structure reduces considerably the amount of, the volume occupied by, and the weight of the concrete required. Consequently, and advantageously so, the quantity of steel reinforcement is lowered, all without diminishing the properties and the characteristics of a conventional step.

Particular attention is given to the configuration of the steps perimeter, which is endowed with unique features for facilitating the erection of a liight and for obtaining a whole gamut of acceptable and suitable liights within the known and conventional equations. The configuration of the perimeter of the steps of the invention enables the determination of the ratio between riser and tread (iiight modulus), so that the sum total of the labor involved in the transportation of the steps may be maintained substantially constant for greater comfort and ease.

By the use of the features of the steps of the invention, it is easy to vary even considerably, during erection of the flight, the ratio between riser and tread, so as to facilitate the completion of each successive iiight and their final iinishing without recurring to constructional makeshifts and improvising, as described hereinafter in greater detail with reference to the accompanying drawings, in which:

FIGURE 1 shows a side view of a typical step shell of ice the invention with reticulated interior and leak-proof compartment for the concrete;

FIGURE 2 shows in side view two step shells as they exit the manufacturing line, each step being readily severable from its mirror-imaged twin;

FIGURE 2a shows one of the two step shells of FIG- URE 2 after having been severed from its twin shell;

FIGURES 3a and 3b show two step shells of FIGURE 1 in assembled position but with different flight inclination, namely, a flight inclination of angle alpha (FIG- URE 3a) and a ight inclination of angle beta (FIGURE 3b);

FIGURES 4a and 4b, similarly to FIGURES 3a and 3b show two step shells assembled in ight position. These shells are of the type given in FIGURE 2a, but are arranged so as to obtain different angular iiight inclinations, namely, an angle alpha prime (FIGURE 4a) and an angie beta prime (FIGURE 4b); and

FIGURE 5 shows another step shell coniiguration.

Referring to FIGURE 1, it can be seen that the perimeter of the step structure has a theoretically visualizable triangular configuration, 1-3'-4-1. However, the theoretical apexes 3 and 4 are truncated: apex 3 is truncated along an oblique plane with respect to the horizontal side 1-3, so that a new and actual side 2-3i is formed in the perimeter of the concrete section, and apex 4' is truncated along two new planes 4-5 and 5-6, of 'which the former is parallel to side 2-3 and the latter is parallel to the horizontal 1 3'.

The body of the step shell has at its barycentric location a unique longitudinal chamber or receptacle having preferably a pentagonal inner configuration 7-8-9-10-11 when the laminar barrier 7-11 is removed. Such removal takes place at the time the step is assembled in ight position and the concrete is ready to be poured therein. This chamber is leak-proof and, after the laminar barrier is removed, the steel reinforcing elements are rst inserted therein, followed by the pouring of the concrete.

The side view of the each twin structure shown in FIG- URE 2a, after severance from the production line (FIG- URE 2) repeats substantially the configuration described with respect to the step shell of FIGURE 1. It can be readily seen that this twin structure is also theoretically triangular and that the truncated apex 103' corresponds generically to the truncated apex 3', while the truncated apex 164 results from the connection of the actual corners 104 and 105 and is parallel to side 10E-103. Here again, in the barycenter of the shell, there can be seen the leakproof unique and longitudinal chamber with configuration 107-108-109-110-111.

In the illustrative exempliiication of an assembly of two step shells (see FIGURE 3a) it can be seen that to the lower (I) shell is superimposed (in juxtaposition with the free and pointed extremity of the horizontal plane 1-2 of I) the equally horizontal heel 5-6 of the upper (Il) shell, obtaining thus mutual support and continuity. A series of shells, superimposed to one another in such a manner, will form a stair liight having an angular inclination alpha between the planes O-A and O O.

This angle alpha is very readily obtained by separating the side 2-3 of shell I from the side 5-4 of the heel of shell II and inserting between the two surfaces a slab 12 of concrete of predetermined thickness.

In the erection of the flight illustrated in FIGURE 3b, although using tne same type of step shells of FIGURE 1, one obtains a flight having a different angular inclination (beta) by simply excluding the insertion of the concrete slab 12.

Analogous reasoning should be applied when referring to FIGURES 4a and 4b as it was applied in the case of FIGURES 3a and 3b. The same results are obtained here by using step shells of different perimetric configuration,`

3 namely, those illustrated in FIGURE 2a and obtained by severance of the twin shells of FIGURE 2.

It should be noted that the steps of the invention may be prepoured individually and not during the assembly of the ght or poured during the assembly of the Hight by lling them from above in a single pouring operation together with the oversailing course in which they are embedded.

Furthermore, the generic and theoretically triangular cross-secti0n of the step shell is not a limitation. Shells answering any technical demand in shape may be readily prepared, as it can be seen from FIGURE 5 of the drawings, in which the shell is rectangularly shaped with opposite parallel truncated apexes.

What is claimed is:

1. In a staircase step shell of cementitious material, having a reticulated hollow interior and being cross-sectionally polygonally shaped, the improvement consisting of a leak-proof, longitudinal chamber located barycentrically within said reticulated interior and having an opening on the tread side of said step shell for the admission of concrete and metallic reinforcing elements.

2. A staircase step shell of cementitious material, having a reticulated hollow interior with a leak-proof, longitudinal chamber located barycentrically therein, said chamber having an opening on the tread side of said step shell for the admission of concrete and metallic reinforcing elements, said step shell being cross-sectionally shaped as a pentagon, two sides of which being at right angle to each other and two other sides of which being parallel to each other, said first-mentioned two sides forming the riser and the tread of said staircase step.

References Cited UNITED STATES PATENTS 2,104,585 1938 Dow 52-609 FOREIGN PATENTS 407,314 1910 France.

83,158 1921 Austria. 379,905 1923 Germany. 542,645 1932 Germany. 262,721 1949 Switzerland. 451,382 1949 Italy. 496,411 1954 Italy. 620,104 1961 Italy. 235,549 1964 Austria.

JOHN E. MURTAGH, Primary Examiner. 

1. IN A STAIRCASE STEP SHELL OF CEMENTITIOUS MATERIAL, HAVING A RETICULATED HOLLOW INTERIOR AND BEING CROSS-SECTIONALLY POLYGONALLY SHAPED, THE IMPROVEMENT CONSISTING OF A LEAK-PROOF, LONGITUDINAL CHAMBER LOCATED BARYCENTRICALLY WITHIN SAID RETICULATED INTERIOR AND HAVING AN OPENING ON THE TREAD SIDE OF SAID STEP SHELL FOR THE ADMISSION OF CONCRETE AND METALLIC REINFORCING ELEMENTS. 